Complete Range of 17-4 PH Lock Nuts

Manufacturing Standards for 17-4 PH Lock Nuts

RAYCHIN LIMITED manufactures 17-4 PH lock nuts to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.

International Standards & Global Designations for 17-4 PH Lock Nuts

To serve clients worldwide, RAYCHIN LIMITED manufactures 17-4 PH lock nuts from material conforming to the following national and international specifications. This ensures full compliance for projects in the Americas, Europe, Asia, and the Middle East.

ASTM A564 GR.630 ASTM A193 GR.630 AMS 5643 1.4542 SUS630 UNS S17400 17-4PH

Chemical Composition (Weight %) – 17-4 PH Precipitation Hardening Stainless Steel

Our 17-4 PH lock nuts are produced from melts that strictly conform to the limits below per ASTM A564 / AMS 5604. The precise addition of copper and niobium enables age-hardening to achieve high strength.

Expert note: The Nb/Cu ratio ensures consistent precipitation of coherent copper-rich clusters during aging. This yields tensile strengths up to 190 ksi (1310 MPa) in the H900 condition while retaining good ductility. All raw material is positively identified by PMI (Positive Material Identification) and certified with mill test reports.

Complete Mechanical Properties of 17-4 PH Lock Nuts (by Heat Treatment per ASTM A564/A564M)

17-4 PH lock nuts are typically supplied in one of eight standard heat treatment conditions. RAYCHIN LIMITED recommends the appropriate temper based on your strength vs. toughness requirements. The data below represent minimum values for the material (longitudinal direction) per ASTM A564/A564M Table 3. Lock nuts are proof load tested to ensure compatibility with mating bolts.

Condition H900 (480°C / 900°F) – Highest Strength

Condition H925 (495°C / 925°F) – Slightly lower strength, improved toughness

Condition H1025 (550°C / 1025°F) – Best combination of strength & toughness

Condition H1075 (580°C / 1075°F) – Improved ductility

Condition H1100 (595°C / 1100°F) – Enhanced toughness

Condition H1150 (620°C / 1150°F) – Maximum stress corrosion resistance

Condition H1150M (760°C + 620°C / 1400°F + 1150°F) – Double aged, maximum ductility (NACE MR0175 approved)

Condition H1150D (620°C + 620°C / 1150°F + 1150°F) – Double aged, improved properties

Additionally, 17-4 PH lock nuts exhibit excellent fracture toughness and very high fatigue strength. Our test certificates include actual values from each production lot. For sour service (NACE MR0175), H1150M or H1150D conditions are recommended for optimal sulfide stress corrosion cracking resistance.

High Temperature Performance of 17-4 PH Lock Nuts

17-4 PH stainless steel is widely used in applications requiring retention of mechanical properties at elevated temperatures. The material maintains excellent strength up to 400°C (752°F), beyond which copper-rich precipitates begin to coarsen. For continuous service, maximum operating temperature is approximately 316-400°C depending on condition.

Temperature-Dependent Strength Retention (Condition H900)

The yield strength of 17-4 PH decreases with increasing temperature, with thermal softening becoming significant above 400°C. For applications requiring strength retention above 400°C, special heat treatments or alternative alloys should be considered. Note that nylon insert lock nuts are limited to 120°C (250°F) maximum service temperature.

Thermal Stability Limits

Corrosion Resistance of 17-4 PH Lock Nuts

17-4 PH stainless steel offers excellent corrosion resistance comparable to 304 stainless steel in many environments, attributed to its high chromium content (15-17.5%) which forms a protective Cr₂O₃ passive layer. The corrosion behavior is significantly influenced by heat treatment condition and aging parameters.

Corrosion Performance in Different Environments

Effect of Heat Treatment on Corrosion Resistance

Critical Corrosion Considerations for Lock Nuts

• Sensitization: Aging above 495°C can cause chromium carbide precipitation at grain boundaries, leading to chromium depletion and increased susceptibility to intergranular corrosion. However, 17-4 PH is generally less susceptible to sensitization than conventional martensitic grades due to low carbon content.
• Stress Corrosion Cracking (SCC): For environments with risk of SCC, use higher aging temperatures (H1150, H1150M, H1150D) which are approved per NACE MR0175.
• Optimal Aging: Solution treatment at 1040°C followed by aging at 480°C for 4 hours provides the best combination of hardness and corrosion resistance.
• Comparison to 304: 17-4 PH offers comparable corrosion resistance to 304 stainless steel in many environments, with significantly higher strength.
• NACE MR0175 Compliance: For sour service applications, only H1150M and H1150D conditions are permitted with maximum hardness of 28 HRC.
• Plating Considerations: For aerospace applications requiring silver or cadmium plating, proper hydrogen embrittlement relief must be performed after plating.

Corrosion Engineering Note: For critical applications in aggressive environments, RAYCHIN LIMITED can provide passivation, specialized coatings (Xylan, PTFE, silver plating), or recommend optimal heat treatment conditions (H1150, H1150M for maximum stress corrosion cracking resistance). Third-party corrosion testing per ASTM G31, G48, or G61 available upon request. NACE MR0175 compliant lock nuts available in H1150M and H1150D conditions.

Why RAYCHIN LIMITED – The 17-4 PH Lock Nut Authority